When a system is installed and started without performing the setup steps for CTM, it will have the default landscape name nolandscape, the default key block range allocation group 3, range 2, and the default CTM system identifier noname.
With these default settings, CTM can only be used in a restricted form. The restriction is that change sets created on the system cannot be transported and applied on any other system. So, a production system setup without performing the CTM setup steps will only allow for usage of CTM subject to these restrictions.
There is further information on the default values for these fields and the associated behaviour in section 5.3 - Setup Tasks.